This C-DEBI Research Exchange was awarded for travel to the ECORD Summer School Course: Subduction Zone Processes hosted by MARUM in Bremen, Germany. This course offered many unique opportunities including networking with international scientists of various disciplines, learning shipboard operations, and improving grant writing abilities. This two-week course surveyed various types of subduction zone environments and included a wide variety of topics including geology, petrology, geochemistry, sedimentology, and microbiology. We participated in small group exercises that surveyed physical properties, core logging, rock geochemistry, downhole logging, core descriptions, thin sections, and temperature and heat flow. Each of these activities were mimicking onboard operations which allowed us to understand how sediment cores were processed on expeditions. This experience allowed me to make numerous contacts with future colleagues and collaborators while also receiving training for future expeditions. This course was relevant to C-DEBI Research Themes 2 (Activities, Communities, and Ecosystems) and 3 (Metabolism, Survival, and Adaptation) because we connected life with surrounding abiotic conditions including geochemistry, geology, petrology, and sedimentology.
The characterization of metabolically active fungal isolates within the deep marine subsurface will alter current ecosystem models and living biomass estimates that are limited to bacterial and archaeal populations. Although marine fungi have been studied for over fifty years, a detailed description of fungal populations within the deep subsurface is lacking. Fungi possess metabolic pathways capable of utilizing previously considered non-bioavailable energy reserves. Therefore, metabolically active fungi would occupy a unique niche within subsurface ecosystems, with the potential to provide an organic carbon source for heterotrophic prokaryotic populations from the transformation of non-bioavailable energy into substrates, as well as from the fungal necromass itself. These organic carbon sources are not currently being considered in subsurface energy budgets. Sediments from South Pacific Gyre subsurface, one of the most energy-limited environments on Earth, were collected during the Integrated Ocean Drilling Program Expedition 329. Anoxic and oxic sediment slurry enrichments using fresh sediment were used to isolate multiple fungal strains in media types that varied in organic carbon substrates and concentration. Metabolically active and dormant fungal populations were also determined from nucleic acids extracted from in situ cryopreserved South Pacific Gyre sediments. For further characterization of physical growth parameters, two isolates were chosen based on their representation of the whole South Pacific Gyre fungal community. Results from this study show that fungi have adapted to be metabolically active and key community members in South Pacific Gyre sediments and potentially within global biogeochemical cycles.